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      • KCI등재

        Aluminum in rocks: Optimized microwave-assisted acid digestion and UV-Vis spectrophotometric measurement

        Nguyen Thanh-Nho,Thai Huynh-Thuc,Le-Thi Anh-Dao,Do Minh-Huy,Le-Thi Huynh-Mai,Le Quang-Huy,Nguyen-Thi Kim-Sinh,Nguyen Cong-Hau 한국분석과학회 2023 분석과학 Vol.36 No.5

        Aluminium (Al) is one of the major elements in rocks and its concentration can be varied, depending on different rock types as well as sources. The present study aimed to propose an analytical method based on the UV-Vis as a cheap, simple, and common instrument equipped in most laboratories for Al quantification in rocks after the microwave assisted acid digestion. The aluminone and 8-hydroxyquinoline were investigated for the colorimetric assay. The results show that the 8-hydroxyquinoline reagent was more favorable in terms of the minimized affects of the potential interferences present in the digested solutions, i.e., Fe3+, Si4+ and F–. The calibration curve was constructed from 0.10 mg/L to 3.00 mg/L with the goodness of linearity (R2 = 0.9996). The limits of detection and quantification (LOD and LOQ) were estimated, i.e., 0.029 mg/L and 0.087 mg/L, respectively. The 8-hydroxyquinoline was applied to real rock samples, demonstrating favorable precision (RSD = 0.34 %-1.8 %) and no remarkable differences were found compared to the inductively coupled plasma-mass spectrometry (ICP-MS) as a reference measurement approach.

      • SCIESCOPUSKCI등재

        Novel Single-State PWM Technique for Common-Mode Voltage Elimination in Multilevel Inverters

        Nguyen, Nho-Van,Quach, Hai-Thanh,Lee, Hong-Hee The Korean Institute of Power Electronics 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.4

        In this paper, a novel offset-based single-state pulse width modulation (PWM) method for achieving zero common-mode voltage (CMV) and reducing switching losses in multilevel inverters is presented. The specific active switching state of the zero common-mode (ZCM) voltage that approximates the reference voltage can be deduced from the switching state sequence of the reduced CMV phase disposition PWM (CMV PD PWM) method. From the reference leg voltages for the zero common-mode voltage, an N-to-2-level transformation defines a virtual two-level inverter and the corresponding nominal leg voltage references. The commutation process of the reduced CMV PD PWM method in a multilevel inverter and its outputs can be simply followed in a nominal switching time diagram for the virtual inverter. The characteristics of the reduced CMV PD PWM and the single-state PWM for zero common-mode voltage are analyzed in detail in this paper. The theoretical analysis of the proposed PWM method is verified by experimental results.

      • KCI등재

        Novel Single-State PWM Technique for Common-Mode Voltage Elimination in Multilevel Inverters

        Nho-Van Nguyen,Hai-Thanh Quach,Hong-Hee Lee 전력전자학회 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.4

        In this paper, a novel offset-based single-state pulse width modulation (PWM) method for achieving zero common-mode voltage (CMV) and reducing switching losses in multilevel inverters is presented. The specific active switching state of the zero common-mode (ZCM) voltage that approximates the reference voltage can be deduced from the switching state sequence of the reduced CMV phase disposition PWM (CMV PD PWM) method. From the reference leg voltages for the zero common-mode voltage, an N-to-2-level transformation defines a virtual two-level inverter and the corresponding nominal leg voltage references. The commutation process of the reduced CMV PD PWM method in a multilevel inverter and its outputs can be simply followed in a nominal switching time diagram for the virtual inverter. The characteristics of the reduced CMV PD PWM and the single-state PWM for zero common-mode voltage are analyzed in detail in this paper. The theoretical analysis of the proposed PWM method is verified by experimental results.

      • KCI등재

        Carrier Based Single-State PWM Technique for Minimizing Vector Errors in Multilevel Inverters

        Nguyen Van Nho,Quach Thanh Hai,Hong-Hee Lee 전력전자학회 2010 JOURNAL OF POWER ELECTRONICS Vol.10 No.4

        In this paper, a novel analysis of a carrier based PWM method for multilevel inverters is presented. The space vector PWM and carrier based PWM correlations in multilevel inverters are investigated in a nominal two-level switching diagram. The obtained results can be applied to design various carrier PWM techniques. In this paper, a carrier based single-state PWM technique, which reduces the switching number and optimizes the active voltage errors, is presented. This PWM technique can be advantageous if there are a large number of levels. The proposed method is mathematically formulated and demonstrated by simulations and experimental results.

      • SCIESCOPUSKCI등재

        Carrier Based Single-State PWM Technique for Minimizing Vector Errors in Multilevel Inverters

        Nho, Nguyen Van,Hai, Quach Thanh,Lee, Hong-Hee The Korean Institute of Power Electronics 2010 JOURNAL OF POWER ELECTRONICS Vol.10 No.4

        In this paper, a novel analysis of a carrier based PWM method for multilevel inverters is presented. The space vector PWM and carrier based PWM correlations in multilevel inverters are investigated in a nominal two-level switching diagram. The obtained results can be applied to design various carrier PWM techniques. In this paper, a carrier based single-state PWM technique, which reduces the switching number and optimizes the active voltage errors, is presented. This PWM technique can be advantageous if there are a large number of levels. The proposed method is mathematically formulated and demonstrated by simulations and experimental results.

      • KCI등재

        Preparation of the Transparent Conductive ZnO Nano Material by Means of Pulsed Spray Pyrolysis

        Pham Hoang Ngan,Nguyen Quang Tien,Do Thanh Dat,Pham Van Nho 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5

        Transparent conductive ZnO lms play an important role in nano science and nanotechnology. Many methods have had various successes in preparing ZnO. In this contribution, we present some results from using a pulsed spray method and subsequent annealing in a hydrogen atmosphere for the preparation of transparent conductive ZnO films. The performances of ZnO produced by using various precursors and in various technology conditions were investigated. We attained ZnO films with sheet resistances below 100 and an average transparency of about 80 % in the visible region of the light spectrum. Those values are of the same magnitude as ones prepared by using other methods. The mechanism of annealing effect in a hydrogen environment is discussed. Transparent conductive ZnO lms play an important role in nano science and nanotechnology. Many methods have had various successes in preparing ZnO. In this contribution, we present some results from using a pulsed spray method and subsequent annealing in a hydrogen atmosphere for the preparation of transparent conductive ZnO films. The performances of ZnO produced by using various precursors and in various technology conditions were investigated. We attained ZnO films with sheet resistances below 100 and an average transparency of about 80 % in the visible region of the light spectrum. Those values are of the same magnitude as ones prepared by using other methods. The mechanism of annealing effect in a hydrogen environment is discussed.

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